Fuel injection pump

ABSTRACT

A fuel injection pump is proposed which has a distributor in which both the injection quantity and the onset of injection are variable. The distributor is axially displaced via electric servomotors and is rotated relative to the drive shaft.

This application is a division of application Ser. No. 243,101, filedMar. 12, 1981, now U.S. Pat. No. 4,406,263.

BACKGROUND OF THE INVENTION

The invention is based on a fuel injection pump for internal combustionengines. In a known fuel injection pump of this kind (German Pat. No.1,303,637), the distributor is actuated by a mechanical regulator inorder to regulate the fuel quantity. This mechanical regulator has aspring packet whose force is arbitrarily Cariable and which acts counterto the force of flyweights. Not only is a mechanical regulator of thistype quite expensive to produce but it is also becoming more and moredifficult due to tightened emission laws to satisfy the fuel injectionrequirements made by engine manufacturers with such a mechanicalregulator.

OBJECT AND SUMMARY OF THE INVENTION

It is the object of the invention to provide a fuel injection pumphaving computerized electronic control of the set-point variable in theinjection system so that the injection can be readily adapted to meetthe most varied requirements of quite diverse engine characteristics,while maintaining the production cost at relatively inexpensive levels.

The invention will be better understood and further objects andadvantages thereof will become more apparent from the ensuing detaileddescription of two preferred embodiments taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified longitudinal section taken through the firstexemplary embodiment, showing only those elements which relate to theinvention;

FIG. 2 is a graphic diagram explaining the function of the invention;

FIG. 3 is a longitudinal section through the second exemplaryembodiment;

FIG. 4 is a cross section taken along the line IV--IV of FIG. 5; and

FIG. 5 is an enlarged sectional view of the coupling element accordingto FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Both exemplary embodiments of the invention are provided with adistributor 2 which is axially displaceable for the purpose of varyingthe fuel quantity. The distributor 2 is disposed so as to rotate withina housing 1 and is to provide with at least two radial pistons 3disposed in this housing 1, which pistons are driven by a cuplike cam 4.A pump work chamber 5 is provided between the distributor 2 and each ofthe pump pistons 3 in constant communication with a longitudinal groove6 disposed on the jacket face of the distributor 2. Branching off fromthis annular groove 6, there are provided a pair of longitudinal grooves7, extending obliquely on the jacket face of the distributor, and adistributor groove 8. A supply bore 9 is controlled by the obliquegrooves 7 and communicates with a fuel source. The distributor groove 8leads to pressure lines 10, which in turn lead to fuel injection nozzles11 disposed on the internal combustion engine.

Because of the oblique disposition of the grooves 7, the supply bore 9is opened for varying time periods in accordance with the axial positionof the distributor 2. As a result, either the effective duration ofinjection varies in length thus determining the fuel injection quantityor the supply bore 9 is allowed to remain open for differing lengths oftime to provide fuel supply during the intake stroke of the pump. Thedistributor groove 8, in contrast, serves to supply fuel sequentially tothe individual pressure lines 10 during the compression stroke of thepump pistons 3.

The cuplike cam 4 is positively connected to a drive shaft 12, whichdrives the distributor 2 via a coupling 13. As a result of this coupling13, the rotary position of the distributor 2 relative to the drive shaft12 is variable; thus the onset of injection of the injection pump isaccordingly variable, because the position of the oblique grooves 7relative to the supply bore 9 is varied as well.

In the first exemplary embodiment shown in FIG. 1, the axial actuationof the distributor 2 is shown schematically. A more specific example ofa possible structure is shown in connection with the second exemplaryembodiment. The distributor 2 is axially adjusted by a servomotor 15having an electromagnet for which a tang 16 of the distributor 2 servesas the armature. The coil 17 of the magnet is connected via a terminal Awith an electronic control device E and is pivoted thereby. Theelectronic control device E, which contains a program based on operatingcharacteristics of the engine, such as rpm, load and the like, receivesactual values on engine state in the form of the position of the gaspedal 18, via a connection to a terminal B. The actual values receivedby the control device, such as gas pedal position, the rpm, temperatureand so on, are processed in the electronic control device E and fed inthe form of a set-point value to the electrical converters, such as theservomotor 15.

The coupling 13 comprises in this exemplary embodiment a magneticcoupling, in which a coil 20 rotates along with the drive shaft 12 andcarries with it in its rotation an armature 21, which in turn transportsthe distributor 2 along rotationally via a universal joint 22. Thedistributor 2 is provided with an oblong slot 23, which is engaged by apin 24 of the universal joint to permit an axial movement on the part ofthe distributor 2, for purposes of fuel quantity variation, which isindependent from the coupling 13. The magnetic coupling 13 is likewisetriggered by the electronic control device E via the terminals C, sothat the onset of injection is effectuated by the relative rotation of arotary magnet or by permitting a follow-up on the part of the armatureof the magnetic coupling. The actual value of the onset of injection isadvantageously measured via the terminals D by a transducer locateddirectly at the injection nozzle 11.

In order to explain the basic function of this pump, a diagram is givenin FIG. 2 in which the stroke s of the pump piston (ordinate) is plottedover the rotary angle α of the drive shaft (abscissa). A curve nrepresents the course of the drive cam 4. After a pre-stroke s₁ has beenexecuted, one of the oblique grooves 7 intercepts the communication ofthe pump work chamber 5 with the supply bore 9, so that the injectionbegins. After an injection stroke s₂ of the pump pistons 3 has beenexecuted, the supply bore 9 is opened once again by the second obliquegroove 7, as a result of which injection is interrupted. The onset ofinjection and the end of injection occur at the rotary angles α₁ and α₂,respectively. During the axial displacement of the distributor 2, theoblique position of the grooves 7 relative to the supply bore 9 isvaried, so that as a result the period of time during which the supplybore 9 is blocked can be changed. The portion of the stroke of the pumppiston 3 which is located between s₁ and s₂ can also be variedaccordingly. Depending on the course taken by the grooves 7, there canalso be a variation of the onset of injection; it may be desired, forinstance, that the onset of injection occur earlier with increasing rpm.A supplementary change in the onset of injection, especially when it isintended that there be no change in fuel quantity, can be attained ifthe distributor 2 is rotated relative to the drive shaft 12. Thisrelative rotation shifts the effective supply stroke action of the pumppistons 3 relating to the onset; an example would be the earlieroccurrence of injection at the stroke portions s_(1') and s_(2'). Inother words, the injection would be allowed to begin at a rotary angleα_(1'). Theoretically, the supply position on the cam curve n is shiftedin its entirety in one or the other direction.

Referring now to the second exemplary embodiment shown in FIGS. 3-5, thedistributor 2 is displaced via a reciprocating magnet 25, which isdisposed parallel to the distributor 2 and acts upon the distributor,via a lever 26, counter to the force of a spring 27. An obliquelongitudinal groove 7 is embodied here as cone-shaped, diverging at oneend to open at the bottom and converging at the other end into a narrowaperture communicating with the distributor groove 8. The pressure linebore 10 is disposed such that it is shifted axially on the circumferencerelative to the supply bore 9; as a result, no fuel can flow out via thebore 9 during the portion of the stroke when injection is taking place.

The coupling 13 is shown on a larger scale in FIGS. 4 and 5. ConsideringFIG. 5 first, the distributor 2 is connected via a pin 28 with a couplerelement 29 provided with flat end sections 30 engaging longitudinalgrooves 31 of a coupler ring 32. The coupler ring 32 is displaced viathe drive shaft 12 and is displaceable thereon counter to the forceexerted by a restoring spring 33 on the cam ring 4 which is rigidlyconnected to the drive shaft 12. Turning now to FIG. 4, the coupler ring32 is carried along in rotation by the drive shaft 12 via a tang 34; toachieve this union rotationally, the drive shaft 12 engages a slightlyhelical longitudinal groove 35 in the inner bore of the coupler ring 32.The distributor 2 and the coupler member 29 are received in an innerbore 36 of the drive shaft 12, and the ends 30 of the coupler member 29protrude toward the coupler ring 32 through recesses 37 in the driveshaft 12. These recesses 37 are enlarged so as to provide for a relativerotation of the drive shaft with respect to the coupler element ordistributor. This relative rotation is effected by the axialdisplacement of the coupler ring 32, which is rotated via the helicalgroove 35 and the tang 34 relative to the drive shaft 12 and thuscarries the distributor 2 along in rotation by means of the couplerelement 29 or, more specifically, by means of the ends 30 and thelongitudinal grooves 31. The coupler ring 32 itself is displaced via alever 38, which engages the ring via a roller 39 and is engaged on theside remote from the ring by a magnet 40 disposed parallel to the magnet25 and to the distributor 2.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other embodiments and variantsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A fuel injection pump for internal combustionengines including a distributor having a jacket face,a coupling means, apump drive shaft to drive said distributor through said coupling means,said distributor having control grooves provided in said jacket face, aninjection quantity regulator means including a first electric servomotorarranged to axially displace said distributor to control fuel quantity,said coupling means comprising a coupler ring means disposed betweensaid drive shaft and said distributor, groove and tang engagement meansbetween said drive shaft and said coupler ring means, said groove beinga helical groove, whereby rotational movement is conveyed by said driveshaft to said coupler ring means upon an axial movement of said couplerring means, said coupler ring means being axially movable by a secondelectric servomotor to effect a relative rotation of said drive shaftand said distributor to change onset of fuel injection, a couplermember-groove engagement is provided between said distributor and saidcoupler ring means, said last mentioned groove being an axial groovepermitting rotational displacement of said distributor independent ofaxial displacement thereof together with said rotational movement ofsaid coupler ring means, and an electronic control device connected tosaid electric servomotors, said electronic control device including acomputer to which engine characteristics are supplied as input, wherebysaid computer triggers said electric servomotors to selectively effectsaid axial displacements of said distributor and said coupler ringmeans.
 2. In a fuel injection pump according to claim 1, in which:anelectromagnet is provided as said second electric servomotor, and alever transmits the electromagnet movement to the coupler ring means.